RECENT ADVANCES IN THEORETICAL LIQUID-CRYSTAL RHEOLOGY

Recent significant advances in theoretical liquid crystalline rheology are presented. Dynamic simulations are performed using a complete the ory which include the three major effects of liquid crystalline materi als: (I) short range order elasticity, (2) long range order elasticity , and (3) viscous flow effects. The results and discussions include re ctilinear simple shear flow, complex non-linear phenomena such as defe ct texture generation and coarsening processes under quiescent and she ar conditions, and pattern formation such as banded texture during and after cessation of flow. The complete theory predicts four in-plane ( 1-D orientation) flow modes and five out-of-plane (2-D orientation) fl ow modes in one-dimensional shear flow, depending on the magnitudes of R (ratio of short to long range order elasticity) and Er (Ericksen nu mber: ratio of viscous to elastic force). The multistability of these flow modes is clearly explained in terms of degrees of freedoms in the nematic orientation. The number of degrees of freedom increases with increasing the spatial dimension of the system, and thus more complex orientation patterns arise in the higher dimension. Well-known defect structures arise and coarsen during simulations of the isotropic to ne matic phase transition. The effect of shear flow on the defect generat ion process is to suppress the defect nucleation, and the simulations suggest a method of how to create defect-free nematic samples. The ban ded textures during and after cessation of flow are also captured by t he complete theory.